Heat resistive coating for metals



Patented Apr. 26, 1938 UNITED STATES PATENT OFFICE No Drawing. Application November 14, 1935, Serial No. 49,789

5Ciaims.

This invention relates to the art of welding and casting, and more particularly to the provision of a mixture or substance for preventing the adhesion of a molten metal to a solid metal, which mixture or substance is easily applied to the surface of the solid metal and tends to preserve the surface of the solid metal to which it is applied.

In the art of welding, as well as in the art of casting and the like, it is often desirable to flow molten metal near or around a surface of solid metal without the molten metal adhering to or in any way harming the surface of the solid metal. That is, in casting, such as in die casting, a molten metal such as aluminum is flowed into a metallic mold where the molten metal'chills and assumes the shape of the mold. In such instances, it is very important in the continuous production of castings that the mold is lubricated to prevent wear thereon and to prevent sticking of the casting inthe mold. It is also important that the mold be protected against pitting, the collection of scale, corrosion, adhesion of the cast or molten I metal to the mold surface, and the like. Likewise, in welding it is often desirable to fiow molten metal up to a certain surface line without having the molten metal cross the line or adhere to the surface of the solid metal across that line.

It is also recognized that the substance used in such instances should not bubble or emit appreciable quantities of gas when subjected to heat, but should form a very thin film that is heat resistive.

It is therefore an object of this invention to provide a substance that can be easily applied to a metallic surface to prevent the adhesion of a molten metal thereto.

Another object of this invention is to provide a substance that will form a very thin film on a metallic surface and withstand heat.

Another object of this invention is to provide a fluid substance that can be easily applied to the surface of a casting mold, and that will preserve and lubricate the surface of the mold.

Another object of this invention is to provide a substance for preserving die casting molds and the like which does not bubble or emit appreciable quantities of gas when subjected to the heat of the casting operation.

Further objects and advantages of the present invention will be apparent from the following description, wherein a preferred embodiment of the present invention is clearly described.

The mixture comprising the subject matter of this invention comprehends a comparatively viscous petroleum product, such as preferably 600 W oil having admixed therewith a lubricating medium such as preferably finely powdered graphite and lime, which is also preferably powdered.

The term 600 W oil is an old and quite generally used term referring to steam cylinder and turbine oils having a fire temperature of 550 to 650 F.; 600 F. being about the average fire" temperature in 2. Cleveland open cup. The viscosity is generally between 120 to 180 Saybolt seconds at 210 F. Although not desiring to be limited at all to a particular oil, because others might be found having the desirable characteristics of resistance to heat and viscosity, this 600 W or steam cylinder oil is given as a preferred and satisfactory grade. More specifically stated, Standard Oil Co. (Ohio) 600 W or steam cylinder oil is understood to have the following characteristics: viscosity-150 Saybolt seconds at 210 F.; fire temperature 605 F. in Cleveland open cup; flash temperature 530 F. in Cleveland open cup.

I It is therefore understood that 600 W oil is an oil having high flash and fire temperatures and relatively high viscosity.

Although not desiring or intending to be limited by any theory as to how and why the substance or mixture accomplishes results, it is advanced that the graphite is a lubricant and the line (C210) is a refractory material and is inert to the metal of the mold or the molten metal. Both the lime and graphite are capable of withstanding relatively high temperatures without bubbling, and both are not harmfully corrosive to the metals. The line being a refractory material greatly reduces the heat transfer from the molten to the solid metal. It is also advanced that the petroleum product or oil serves as a suspending medium or carrier for thegraphite and lime, and as such is preferably sufliciently viscous to carry, or hold, the lime and graphite in suspension.

In preparing the mixture, the recommended proportions are approximately one pound of powdered graphite and two pounds of lime to one gallon of oil. It is understood that other proportions could be used without departing from the spirit of the invention. The ingredients are preferably thoroughly stirred when mixed and when used, and with the preferable proportions set forth above, the mixture will flow. Flowability is desirable, because it can then be applied to mold or surface more easily.

When used on molds such as casting dies, the mixture is preferably sprayed on, so that a very thin film covers the molding surface. When used to prevent the adhesion of molten metal to a surface, when welding, the surface is coated with the mixture, as by painting up to the line where the flow of metal is to be stopped. It can be wiped oil? after the welding is completed.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming withinthe scope oi. the claims which follow.

What is claimed is as follows:

1. As a preservative for casting dies and the like, 600 W oil, powdered graphite and lime mixed in substantially the proportions of one gallon of 600 W oil to one pound of powdered graphite to two pounds of lime.

2. As a preservative for casting dies and the like, 01] having high heat resistive qualities, graphite and lime mixed together in proportions that provide a viscous fluid mixture, the lime content of which mixture is approximately twice the graphite content by weight and the oil content is approximately two and one-half times the graphite-lime content by w ght.

3. A preservative and lubricant for casting dies and the like comprehending a lubricant comprising graphite, a refractory material comprising powdered lime, and a relatively viscous oil as a carrying medium mixed approximately in the proportions of one pound of graphite to two pounds of lime to one gallon of carrying medium.

4. A preservative for casting dies and the like, comprising a viscous oil having high heat resisting qualities, graphite and lime mixed together, the graphite and lime contributing about onethird by weight of the mixture and standing "in the relation of one to two respectively.

5. A preservative for casting dies and the like, comprising oil characterized by a fire temperature of 550 to 650 F., powdered graphite and lime, the constituents standing in the approximate relation by weight of seven and onehalf (7%), one (1), and two (2), respectively.

GEORGE W. SMITH. 

